His comments came as party delegates overwhelmingly passed a motion calling for a second referendum on the final terms of Brexit.

Party leader Mr Farron said: "“The Liberal Democrats are now the only party who will give the public a vote on the final deal and who will campaign to remain in the EU."

But Sir Vince said: “What happens if you win? Is that binding? Do you have to do a third?

“Which side would we be on if there was a soft Brexit? Would we support Theresa May or would we be with Nigel Farage voting it down?”

He added: "I don't think it should be the issue we're leading on.

"I'm not criticising [Mr Farron], I would just like to see more emphasis on what it is we want from these negotiations rather than arguing about the tactics and the means.

"We must accept the public have voted on the matter. We have to negotiate and we have to set out what are the things we should make some concessions on, and freedom of movement is one, and what are things we're fighting for."

Former Lib Dem leader Paddy Ashdown also seemed to put himself at odds with Mr Farron by saying the verdict of the British people must be respected.

He said: "We accept the British people's judgement, but if we're going to be out we need to be as close to Europe as possible. The Lib Dem position remains that given a choice between in and out, we would like to go back in, but we don't have that choice."

Earlier today, former deputy prime minister Nick Clegg warned the Conservatives would never be able to call themselves a “responsible party of government” if they take the UK out of the European single market.